The present invention relates to means for facilitating the spline interconnection between the opposing ends of the axially inwardly extended driving shafts of driving gears of coaxialy disposed pump or motor units and more particularly improvements in or relating to gear pumps or motors, whereby in assembly the correct axial alignment and spline connection between the opposing driving shafts thereof may be facilitated.
The gear pump comprising two pump units which are substantially indentical in structural and functional features is disclosed in as for example U.S. Pat. No. 3,101,673, granted to H. M. Clark et al, Aug. 27, 1963 (British Pat. No. 982,014). Each pump unit comprises a casing member and a cover member, and a pair of intermeshing gears are disposed in the pumping chamber defined in the casing member. The axially outwardly extended shafts of the driven and driving gears are journalled in the cover member while the axially inwardly extended shafts thereof are journalled in the casing member itself. The radial mating surfaces of the two casing members are formed with recesses, which define a space when assembled, and with axial holes or bores for receiving locating or dowel pins. The two pump units are assembled together with the axially inwardly extended driving shafts into the space splined to each other with an internally splined sleeve.
The gear pump or motor of the type described above has some defects. First, when the opposing driving shafts are splined together, they must be correctly aligned in coaxial relationship. Consequently, the shaft holes or bores of the casing members must be correctly aligned. To this end, the locating holes and locating or dowel pins must be machined with a higher degree of accuracy so that highly skilled and experienced operators, high-precision machines and many machining steps are inevitably required, thus resulting in the increase in manufacturing cost. Second, in order to spline the driving shafts to each other with the internally splined sleeve, two separate or split casing members must be used and aligned correctly with respect with each other with the use of locating or dowel pins. As a result, the number of parts is increased, resulting in the increase both in material and fabrication costs.